Cottonscope: A New Instrument for the Rapid, Direct Measurement of Cotton Maturity
March 31, 2010 Cotton maturity is an important fiber property that has proved difficult to measure accurately and quickly. Immature cotton fibers are weaker and more likely to break and cause neps when processed. They also absorb less dye so that they appear a lighter shade in dyed fabric.
The micronaire instrument measures the combination of fineness and maturity. Unfortunately, the same micronaire result can be obtained for a fine, mature sample as for a coarse, immature sample. This inhibits the development and breeding of better cotton that the industry needs to compete against other fibers. Hence, development of a rapid and accurate maturity measurement instrument is a high priority.
It was discovered in the 1930s that cotton fibers would appear different colors when viewed by a microscope using polarized light. This led to a standard maturity test, ASTM D1442. However, this test has a significant problem in that operators interpret the colors differently, which reduces the repeatability of the maturity measurement.
In 2003, Dr. Stuart Gordon and his team at Australia’s government research agency, the Commonwealth Scientific and Research Organization (CSIRO), with the financial assistance of the Australian Cotton Research and Development Corporation (CRDC), began developing an instrument called SiroMat that overcame the problem of manual color measurement by using a digital video camera mounted on a microscope.
The combination of the SiroMat and Optical Fibre Diameter Analyser technology became the Cottonscope instrument. Cottonscope is a fully automated microscope that uses polarized light to capture color images of cotton snippets on a glass slide. In the image, the fibers appear different colors against a magenta background; the immature fibers are blue or orange, and the mature fibers are yellow or green. The yellowness of each snippet is then used to calculate the maturity ratio. A slide of 3,000 to 5,000 cotton snippets is measured in 25 seconds.
A major breakthrough is the removal of the requirement to use mounting liquid for the fibers. The dry fiber mounting method allows rapid preparation and cleaning without mess. Cotton snippets approximately 1 millimeter long are cut from the sample using either a guillotine or a minicore, spread onto a glass slide using an automatic spreader and then vacuumed off after measurement.
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